Non-woven fabrics by electrodeposition

ABSTRACT

NON-WOVEN FABRIC WEBS OF FIBER AND BINDER RESIN ARE FORMED AT ONE ELECTRODE OF AN ELECTROLYTIC CELL FROM A DILUTE BATH OF FIBERS AND RESIN IN AQUEOUS SUSPENSION. SOFT, PLIABLE WEBS ARE OBTAINED BY USING VERY DILUTE SUSPENSIONS HAVING LESS THAN ONE PERCENT BY WT. FIBER AND LESS THAN 0.2 PERCENT BY WT. RESIN IN THE AQUEOUS COATING BATH AND HAVING ONE TO FIVE PARTS FIBER PER ONE PART RESIN IN SAID BATH.

United States Patent 3,699,028 NON-WOVEN FABRICS BY ELECTRODEPOSITIONRobert Edward Torley, Wilton, and Richard Dale Bankert, Norwalk, Conn.,assignors to American Cyauamld Company, Stamford, Conn. No Drawing.Filed Oct. 1, 1971, Ser. No. 185,875 Int. Cl. B01d 13/02; B01k 5/00;C23b 7/00 US. Cl. 204-180 R 8 Claims ABSTRACT OF THE DISCLOSURENon-woven fabric webs of fiber and binder resin are formed at oneelectrode of an electrolytic cell from a dilute bath of fibers and resinin aqueous suspension. Soft, pliable webs are obtained by using verydilute suspensions having less than one percent by wt. fiber and lessthan 0.2 percent by wt. resin in the aqueous coating bath and having oneto five parts fiber per one part resin in said bath.

The invention relates to manufacture of non-woven fabrics and articlesof such fabric by electrophoretic deposition from aqueous dispersions offiber staple or flock dispersed in aqueous bath with resin binder.

Non-woven fabrics of fiber staple and flock have been made by severalmethods, usually by depositing the fibers in a suitable paper makingmethod or in a dry lay process and subsequently impregnating the depositof fibers with resin binder.

The invention provides improvements in electrophoretic coating processwhereby the electrophoretic process is adapted to the making ofnon-woven fabrics having properties that are comparable with and in someinstance superior to those non-woven fabric products of the paper makingand dry lay processes.

Electrophoretic coating methods have been used successfully for applyingresin and pigment paint to metal and other conductive surfaces such aswires, plates, screens and the like. In addition to ordinary pigments,other solid materials such as carbon, graphite and asbestos fibers,mica, and the like have been included in the electrophoretically coatedmaterial with suitable resins. Not all electrophoretic processes havethe purpose of painting or insulating the electrode surface.Electrophoresis has been used for forming sheets, films and the like onan electrode, from 'which the deposited sheet or film is then removedfor use as such apart from the electrode. US. Pat. No. 3,449,227,patented June 10, 1969 to G. F. Heron et a1. describes anelectrophoretic process for making sheets, tapes, yarns and the likewith asbestos fibers or other mineral fibers. The process of the presentinvention differs from the process described in the Heron patentessentially by substantial differences in the concentrations of theresin and the relative concentrations of resin and fiber materials inthe electrolyte baths that are used in the respective processes. Becauseof those essential process differences, and because the presentinvention may use other fibers than asbestos, the non-woven fiberproducts are of substantially ditferent texture and composition than theproducts described in the Heron patent.

The invention produces non-woven fiber sheets or articles which areessentially self-supporting fabric webs of synthetic and naturalcellulosic fiber staple or flock, or the like, or mixtures of suchstaple and flock fibers, bound with a synthetic resin binder. Thisself-supporting web material in some of our most perferred embodimentshas a fleecy or flocculent outer surface but in several embodiments thefabric products may be modified in texture, thickness, density, porosityand permeability to some extent by variations in the selection ofmaterials and by variation of the process conditions and byafter-treating methods such as curing and calendering. The fabricproducts have sufiicient dry strength to be self-supporting for manyuses, but are also adaptable for fabrication with a scrim or backingmaterial for additional strength if desired. The invention has theadvantage that in some embodiments shaped articles of fabric can beformed directly to a desired shape by electrodeposition of the fabric ona suitably shaped electrode mold. Fabric sheets, tubes, tapes, cups,preformed articles of clothing, and other shaped fabric articles such asirregular shaped toys, mitts and the like can be formed directly bydeposition of the fiber and binder on shaped electrode surfaces andremoving the formed articles from the electrode. The web fabric attainsstructural integrity and some wet strength as it is formed on theelectrode due to the presence of resin binder in the web fabric. Theprocess is especially advantageous for making disposable non-wovenfabric articles such as disposable towels, napkins, sheets, clothes andthe like.

In a process according to the invention, an aqueous suspension isprepared comprising dispersed synthetic fiber staple or flock or amixture thereof suspended in the bath and synthetic resin binder whichis either coated on the fiber surfaces in some embodiments, or moreoften is present suspended as finely divided resin particles dispersedin the aqueous electrolyte bath. The suspension usually will alsocomprise a soluble emulsifying agent to maintain the fiber and binder inthe dispersion. However, in a few instances the binder resin may possessinherent surface active properties adequate for this dispersingfunction. Immersed in the aqueous bath is a working electrode on whichthe fiber and resin are to be electrophoretically deposited. Usually butnot in all instances the working electrode is the anode. A counterelectrode of opposite polarity will also contact the aqueous suspension,separated from the working electrode, to complete the cell. Theelectrodes are connected electrically to a direct current external powersource and current is supplied at voltage suflicient to cause the fiberand resin to be co-deposited at the working electrode.

After the desired fabric of fiber and resin has been formed byelectrophoretic deposition on the anode, the fabric is stripped from theelectrode. In some embodiments the electrode is removed from thesuspension and the fabric is dried before removal from the electrode. Inother embodiments, particularly when the web has sufiicient wetstrength, it can be stripped wet from the electrode and then dried.

Preferred fibers for use in the invention are fine denier syntheticresin staples and flocks of lengths ranging from about microns upwardsto about two inches in length. Preferred fibers are staples of lengthfrom about 4; inch to about one inch and of denier in the range fromabout one to about 15 denier. Mixed fibers of varying denier or ofvarying lengths within the defined ranges, or of both mixed denier andmixed lengths may be employed for varied fabric effects. The fibers maybe flocks, staples, strands, filaments, etc. of any of several syntheticresin materials. Suitable synthetic fibers include polyesters such aspoly (ethylene terephthalate), poly(dimethylenecyclohexaneterephthalate) and the like; viscose fibers such as rayon; polyamidessuch as the nylons; acrylic fibers such as polyacrylonitrile andmodacrylic fibers and the like. Other fibers than the synthetic ones,such as mineral fibers and cellulosic pulps maybe employed in otherembodiments of the invention. The selected fibers must be capable ofbeing dispersed in the aqueous suspension, and should have a surfacecharge associated with each fiber.

Also dispersed in the aqueous suspension with the fibers is a binderwhich also carries a charge so that it is also attracted to theelectrode. Usually the binder is in suspension as in a colloidaldispersion or latex of resin particles but in some embodiments thebinder resin is carried on the surface of the fibers in the suspension.For anodic deposition, the fiber and binder will both be chargednegative (anionic) and usually, but not in all instances, this charge isimparted by the action of an anionic surface active agent which is alsoin the aqueous medium. In other embodiments the suspended materials maybe all charged positive for deposition at the cathode. In thoseembodiments, cationic resins and surfactants would be employed. In thefollowing descriptions the more preferred anionic depositions aredescribed in detail. However, the invention may be used for cationicdeposition by using cationic resins and surfactants.

In those embodiments that employ dispersed resin particles separatedfrom the fibers in the suspension, the selected resin is one that willcoagulate or precipitate by being discharged at the anode, preferablybeing deposited as a wet gel or adhesive which provides a coheringbinder for the wet deposit of fibers, and which becomes the dry fabricbinder upon drying. Aqueous suspensions of resins suitable for depositat the anode are latex suspensions of acrylic acid homopolymer orcopolymers thereof with other acrylate or styrene monomers, ofpolyurethane resins or the like, of polyvinyl latex such as polyvinylchloride, and a carboxy modified butadiene/acrylonitrile copolymers suchas Hycar 1572 and the like.

In those embodiments having the resin coated on the fibers insuspension, suitable resins for the purpose include resins forelectrocoating paints in volatile, non-aqueous solvents such as CyanamidXE-4010 Resin which is a solution of styrene-alkylacrylate-acrylic acidcopolymer in a volatile nonaqueous solvent.

The concentration of both the fibers and the resin in the aqueouscarrier are very important factors determining the consistency of thefabric that will be formed by electrophoretic deposition. To make aloosely matted, porous and permeable non-woven flocculent fabricaccording to the present invention, we employ aqueous dispersions havingabout one-fourth percent to about one percent by weight of the finedenier fibers in suspension and having about 0.05 to 0.2 percent byweight of resin solids in the suspension. It is important to keep thefiber suspension sufficiently dilute to avoid fiber entanglement andconsequent coagulation of the fibers in suspension. Furthermore, andmost important to the invention, it is necessary to Work with the verydilute baths in order to obtain a desired high fiber to binder ratio inthe fabric product. The fiber to resin ratio (by weight) in the aqueouselectrolyte suspension is usually in the range from about two to aboutfive parts by Weight fiber to one part binder. Too little resin inrelation to the amount of fibers will cause defective bonding of thefabric and too much will produce too dense a resin deposit. At higherconcentrations of fiber in the suspension the fibers tend to tangle andcoalesce, causing uneven deposits of fibers in the fabric.

The electrodeposition rates of the several sizes and kinds of fibers andof various resins in the aqueous suspension usually will vary, with theresult that the relative proportions of the same elements in the fabricdeposit will not usually correspond directly to their relativeproportions in the aqueous suspension. Generally, it is found that in asuspension of mixed fiber lengths, shorter fibers tend to deposit at afaster rate than longer fibers of the same denier. Also, the fibersgenerally tend to deposit at rates slower than the deposition rates forthe binder resins (except in those embodiments where the binder is boundto the fiber surface in the suspension). The result is that for a givencomposition of the suspension, the relative proportion of fiber tobinder usually will be lower in the deposit than the proportion of fiberto binder in the suspension (with the exception already noted) and thesame is usually true of the relative proportions of shorter and longerfibers when mixed fibers of several lengths are used.

Fabrics made in accordance with the present invention have much higherfiber to binder ratios than the fabric deposits described in theaforementioned Heron patent, and it was an object of the presentinvention to provide a process that could produce evenly depositednon-Woven fabrics with fiber to binder ratios high enough to avoid thestiff, non-porous texture caused 'by higher resin concentration. It wasfound that such high fiber to hinder ratios in the deposited fabric areobtained only by using dilute aqueous dispersions having not more thanabout one percent fiber and not more than about 0.2% resin in theelectrolyte bath.

Most of the aqueous dispersions of resins that are commerciallyavailable have been provided with an anionic surfactant as an emulsifieror dispersing agent for dispersion of the resin solids in a latex. Insome instances the pressence of no more than this already providedamount of surfactant in the total suspension is found to be sufficientto act also as a dispersant and charge agent for the fibers. In mostcases however, the presence of an additional amount of the same oranother anionic surfactant will be needed to provide a surface chargefor the fibers in suspension. When necessary, the fibers can beprecoated with a concentrated surfactant to further assist fiberdispersion as the precoated fibers are stirred into the aqueous bath. Insome instances the fibers are precoated with an insoluble resin binderwhich remains fixed on the fiber surface after the coated fibers aredispersed in the bath. A particularly suitable class of anionicdispersion agents for dispersing the fiber and binder in the bath arethe high molecular weight polyacrylic acid having molecular weightranging from about 5 to about 15 million. In addition to its dispersingfunction in the bath, this agent also behaves as a binder and therebyimproves the wet and dry strength of the fabrics.

Effective concentration of the dispersion agent, when used, will be wellbelow 0.1 percent of the total weight of the aqueous suspension andusually will be in the range from about .001 to .01 percent by weight.

In the cell, the working electrode surface may be any suitableelectrically conducting material such as carbon, noble metals, otherconductive metals that are electrochemically inactive or non-noblemetals which are electrochemically active. The latter metals when usedat the anode will be ionized in the aqueous medium to some extent duringthe electrodeposition and this may affect the depositioncharacteristics, particularly the coagulation of resins. Such anodemetal ionization effect is not essential to the invention, but it may bepresent, and even may be advantageous in some cases. It is preferable toselect an electrode with a smooth polished surface to facilitate removalof the fabric deposit from the electrode. Aluminum is found to be ananode that is quite suitable for the purpose in all respects and is mostparticularly advantageous because of its relative economy. Othersuitable electrode materials include iron and steel and particularlystainless steel, as well as copper, zinc, cadmium, nickel and the like.The electrode for deposition may be shaped to the desired shape of thefabric product. For making fabric sheets, a plate or cylindricalrotating drum or a continuous metal belt may be employed as theelectrode. For making continuous tubing, a cylinder electrode ofsuitable length may be provided, immersed in the aqueous bath with meansfor continuously drawing the formed fabric tube from one end of thecylinder. Individual articles such as cups, mitts, stocking shapes andthe like can be formed on appropriately shaped individual electrodes.The counter electrode may be any suitable electrode material and in apreferred embodiment, the metal walls of the tank holding theelectrolyte bath is the counter electrode.

The operating voltgage is selected to be high enough for suitably rapiddeposition, but not so high as to cause excessive electrolysis withconsequent excessive gas formation. Optimum voltage will usually be inthe range from about 90 to about 200 volts and most often about 125-17volts, varying within the range according to the selected electrodes andthe composition of the bath. Some slight electrolysis at the workingelectrode is necessary in some embodiments to generate positive ions forreaction with the suspended particles near the electrode surface. Forexample, at the anode, hydrogen ion generated by electrolysis willdiffuse outward into the deposits and discharge some of the attractedparticles that have not reached actual contact with the electrodesurface.

It is possible to vary the texture, thickness, strength, porosity,appearance, etc. of the web fabric products by varying the selection offiber and resin materials and the selection of process conditions withinthe ranges already described. Generally, strength of the fabric isincreased as fiber length is increased and as resin concentration isincreased and as deposition voltage increases. Longer fibers tend todeposit less evenly than short fibers and the fabric of short fiberstends to be more densely packed and less porous than the fabrics oflonger fibers. Increasing the proportion of resin to fiber will cause astronger, denser and less porous product. Thickness of the deposit willdepend mostly on the processing time, applied voltage and theconcentrations of fibers and binder in the bath. Deposits from about 5mils up to about one inch thick can be made in some instances, but formost uses fabric thicknesses of about 30 mils to about 4; inch thickwill be preferred. We prefer to use fine denier fibers to obtain a soft,pliable fabric. Fibers heavier than about 15 denier will result in verycoarse fabrics.

Natural fibers such as wood pulp, wool and some mineral fibers havefibrils which would act as tiny hooks to make the fibers self-bonding ina web, and in some instances hydrogen bonding can take place withfurther increased strength, but the synthetic filaments used in thisinvention do not have such self-bonding characteristics, so it isespecially necessary to provide a well dispersed bonding resin withinthe fibrous web. Without a binder in the suspension, the synthetic fiberwould gather at the electrode but would fall away when the electriccurrent was stopped. The most even distribution of fiber and resinthroughout the fabric is obtained by precoating the fibers with a resinbinder that imparts a surface charge on each fiber. When separate resinlatex particles and fibers are dispersed together, the resin depositedin the fabric will tend to be most concentrated at the fabric sidenearest the electrode and the proportion of binder to fiber will tend todiminish outwardly through the fabric.

In some embodiments, particularly when mixed fiber lengths are used, itis found that the web product will vary in composition from a relativelysmooth inner surface nearest the electrode where shorter fibers and moreresin predominate, outwardly to a fiocculent or even fieecy outersurface where the longer fibers are more dominant. This range ofcompositions across the fabric cross-section is in some instances anadvantage because the inner, denser part of the web provides relativelymore fabric strength while the outer surface has a more decorative andornamental appearance.

EXAMPLE I Five grams of inch long 3.0 denier polyester fiber, 2.5 gramsof inch 9.0 denier rayon and 1 gram /1 inch 3.0 denier rayon are soakedfor 15 minutes in 250 ml. of a .01 Wt. percent aqueous solution ofAerosol OT 75 (American Cyanamid Company) anionic surfactant. The fibersare removed from the solution, partially dried, then dispersed in 4500ml. of a dilute aqueous latex which is prepared by mixing the followingwith water to make 4500 ml.:

3.5 ml. of a 45% solids latex of a copolymer of styrene and mixed loweralkyl acrylate and methacrylate esters (Accobond 1094, American CyanamidCompany).

0.35 gram of hexamethoxymethylmelamine as a crosslinking agent for thestyrene-acrylate copolymer.

56.1 ml. of 10% solids aqueous emulsion of anionic polyurethane resin.(Cyanoboncl U270, American Cyanamid Company).

0.075 gram of polyacrylic acid (M.W.-15 million).

Final composition of the bath in wt. percent was:

Percent Fiber 0.185 Cyanobond U270 polyurethane 0.12 Accobond 1094 0.03Hexamethoxymethylmelamine 0.001 Polyacrylic acid 0.002

Remainder water.

The suspension was circulated from a reservoir through a 4 inchdiameter, 5 inch deep stainless steel plating chamber by means of aRandolf pump. The plating chamber walls served as the cathode. The anodeform on which the fabric was deposited was an aluminum cup 1%; inch indiameter and 2 /2 inch long. The cup was sprayed on its outer surfaceswith Releasagen HIS-1 prior to immersing it in the bath. Uponapplication of v. across the anode and cathode a deposit began to form.The voltage was applied for 4 minutes after which time the coated anodewas removed from the bath, washed in water and dried at 70 C. forone-half hour. The deposit was removed from the form easily and had adry weight of 1.17 grams and an average thickness of .030 inch. Theproduct is a porous, non-woven fabric cup which is flexible as cloth butable to recover its original shape. It has a soft, fleecy outer surfaceand a somewhat smoother inner surface.

EXAMPLE II This embodiment employs fibers dispersed with the binderresin fixed to the surface of the fibers in the electro-coating bath.

Seventeen grams each of 4: inch long, 3.0 denier polyester fiber and 4inch 9.0 denier rayon fiber are soaked in a 7.5 wt. percent solution in2-ethoxyhexanol of XC401O (American Cyanamid Company) acrylic resin.This resin is an acrylic copolymer having acrylic acid groups in thepolymer chain. The fibers are removed from the resin solution, blotteddry and then vacuum dried at 25 C. overnight to remove the solvent. Theresin-coated fibers are thoroughly beaten in 2 liters of water by aWaring Blendor and then added to a plating tank containing 2.5 liters ofwater. Approximately 1 cc. of diethylamine is added to the bath topartially neutralize the carboxyl groups on the acrylic acid resin andthereby provide a good dispersion. Electrical conductivity of the bathis 7.4 10- ohm" cmr- The anode form and plating chamber are the same asdescribed in Example I. Upon application of 150 v. for two minutes,electrophoretic deposition of the fibers forms a fabric cup on theanode, which is stripped from the electrode, washed in Water and driedat 70 C. for onehalf hour. Dry weight of the fabric cup is 0.43 gram andthe fabric walls are 0.010 inch thick.

EXAMPLE III A bath was prepared using the same materials and procedure,but only half the binder concentration described in Example I.Composition of the fresh bath before electro-deposition was:

Percent Fiber .18 Cyanobond U270 .06 Accobond 1094 .02Hexamethoxymethylmelamine .0005 Polyacrylic acid .002

A deposit was formed at 150 v. for 4 minutes onto an aluminum anode cup1 inch in diameter and 2 /2 inch long. The dry deposit weighed 1.85grams and had an average thickness of 0.050 inch. The deposit was softerbut had less strength than that produced in Example I due to thedecreased binder content.

EXAMPLE IV A bath was prepared using the same materials and proceduredescribed in Example I but having only 30% of the binder concentrationdescribed in Example I. The bath composition was:

Percent Fiber .18 Cyanobond U270 .036 Accobond 1094 .0012Hexarnethoxymethylmelamine .003 Polyacrylic acid .002

Upon application of 150 v. across the cell for 4 minutes a depositformed on the surfaces of the aluminum anode cup. The deposit had verylow wet strength due to the low binder concentration.

EXAMPLE V A bath was prepared using the same materials and procedure butabout twice the total fiber concentration as in Example I. The finalbath composition was:

Remainder water.

A deposit was formed at 150 v. for 2 minutes on an aluminum cup 1 inchin diameter and 2 /2 inch long. The deposit had an average thickness of.030 inch.

EXAMPLE VI This example is presented for comparison to illustratecertain advantages of the invention. A more concentrated bath wasprepared by adding 12.2 g. A inch 9.0 denier rayon and 52.2 g. rayonfloc to 2375 ml. of an aqueous latex to make a final bath compositionof:

Percent Fiber 2.6 Cyanobond U270 0.51 Accobond 1094 0.45Hexamethoxymethylmelamine .015

Remainder water.

A deposit was formed on a 3 inch x 3 inch aluminum anode plate at 100 v.for 2 minutes. Dry weight of the deposited sheet removed from theelectrode was 4.64 grams. The sheet had very uneven surface texture andwas very stifi with more of the character of the polymeric binder thanof the fibers.

EXAMPLE VII In this example, the process produces a non-woven fabrichaving a gradation of polymer to fiber ratios across the thickness ofthe fabric with substantially more polymeric binder deposited at theinner side nearer the electrode than on the outer side of the fabric.

A bath is prepared by the procedure described in Example I, butcontaining 12 grams rayon flock, 5.9 grams of A1, 3.0 denier polyesterfiber, 4.4 grams of A", 3.0 denier rayon fiber and 140 ml. of a solidslatex Cyanobond 4270 in 10 liters of deionized water. The composition ofthe bath in wt. percentage is:

Percent Fiber 0.22 Cyanobond 4270 0.14

Remainder water.

The deposit is formed by electrodeposition in the same manner describedin Example I. The fabric is deposited on the positive electrode, a 2 /2"diameter, 5" long aluminum cylinder which has been sprayed withReleasagen Hl5-1. The electrodeposition is carried out using 200 voltsconstant voltage for 3 minutes. The electrode is removed from the bathand the deposit is washed in deionized water while still on thecylinder. It is then carefully removed wet from the cylinder and drumdried for 4 minutes at 120 C. The fabric, which is about 30 mils thick,is soft and flexible and has a. gradation of polymer to fiber ratiothrough the thickness of the fabric 'with the electrode side havingrelatively more polymer than the fleecy outer surface. This gradation ofpolymer to fiber ratio is visibly apparent by no more than visualobservation of the two sides. The electrode side is smoother andstronger than the fleecy outer side. A photomicrograph of a crosssection of the fabric shows the gradation of polymer concentrationacross the thickness of the fabric. The average composition of theentire fabric is measured and found to be 42% Cyanobond 4270 and 58%fiber. The fleecy outer side of a 1.29 g. sample of the deposit isabraded to remove material from the fiber-rich outer surface. Thismaterial is analyzed and found to contain practically all fibers with noappreciable amount f0 polymer. Material abraded from the polymer richside, the side deposited nearer the electrode, was analyzed and found tocontain 54% Cyanobond 4270 and 46% fiber, which is higher than theaverage polymer concentration. These tests and observations demonstratethe gradation of polymer concentrations across the thickness of the web,from a concentration well above average on the inner side to nearly allfibers at the outer surface. Also the micrographs clearly show gradualdeposition of higher proportions of the longer fibers outward from theelectrode side.

The foregoing examples illustrate several embodiments of the invention.These and various other embodiments of the invention have producedfabrics having tensile strengths '(dry) from about 2 to about 19 poundsper inch. Variations and modifications of the invention which are notspecifically described may be made within the scope of the invention asit is described herein and defined by the following claims.

We claim:

1. A process of making non-woven fabric articles comprising depositingfibers and resin by application of a suitable voltage at an electrodesurface from an aqueous bath in which such fibers and resin aredispersed and removing the fabric deposit from said electrode, the fiberin said bath being present at concentration less than one wt. percentand the resin in said bath being present at concentration less than 0.2wt. percent, said percentages based on the total weight of the aqueousbath, and the wt./wt. ratio of fiber to resin being in the range fromone to five parts fiber to one part resin in said bath.

2. A process defined by claim 1 wherein said fibers are of length in therange from about microns to about two inches and of denier in the rangefrom about 1 to about 15 denier.

3. A process defined by claim 2 wherein said fibers are synthetic resinfibers.

4. A process defined by claim 1 wherein said fiber and resin aredispersed with the resin fixed to the surface of said fibers in thedispersion.

5. A process defined by claim 1 wherein the ratio of fiber to hinderobtained in the fabric deposit is in the range from about one to aboutfive parts by weight fiber to one part resin in the fabric deposit.

6. A fabric made by the process defined in claim 1, having a gradationof polymer to fiber ratios across the fabric cross section.

7. A fabric made by the process defined by claim 1 having dry tensilestrength in the range from about 2 to about 19 pounds per inch.

8. A fabric made by the process defined by claim 1 FOREIGN PATENTShaving thickness in the range from about 30 to about 953,506 7/1962Great Britain 204 16 125 1,070,343 6/1967 Great Britain 20416 ReferencesCited OTHER REFERENCES 5 JOHN H. MACK, Primary Examiner 2,858,25610/1958 Fahnoe 2044 I v 3,061,525 10/1962 Grazen 204 16 T- TUFARIELLO,Assistant Exammer 3,449,230 6/1969 Heron et a1. 204180 R Cl.

3,449,227 6/1969 Heron et a1. 204-180 R 10 204 4 181 3,556,969 1/1971Mizuguchi et a1. 204180 R 3,626,041 12/1971 Fields 204-180 R

